wip modernize/continue implementation

- Adds is_void_v.

- Uses enable_if to disable operator* and operator[] for void types.

- Uses the new school C++-compatible atomic hack.

- There is no implicit conversion from raw pointers to unique_ptr.

Test compiles and passes now.

ctl/is_void.h

@@ -19,6 +19,9 @@ template<typename _Tp>
 struct is_void : public is_void_<typename ctl::remove_cv<_Tp>::type>::type
 {};
 
+template <typename T>
+constexpr bool is_void_v = is_void<T>::value;
+
 } // namespace ctl
 
 #endif // CTL_IS_VOID_H_

ctl/shared_ptr.cc

@@ -23,7 +23,7 @@
 namespace {
 
 inline void
-incref(_Atomic(size_t)* r)
+incref(_CTL_ATOMIC(size_t)* r)
 {
     size_t r2 = atomic_fetch_add_explicit(r, 1, memory_order_relaxed);
     if (r2 > ((size_t)-1) >> 1)
@@ -31,7 +31,7 @@ incref(_Atomic(size_t)* r)
 }
 
 inline int
-decref(_Atomic(size_t)* r)
+decref(_CTL_ATOMIC(size_t)* r)
 {
     if (!atomic_fetch_sub_explicit(r, 1, memory_order_release)) {
         atomic_thread_fence(memory_order_acquire);
@@ -41,7 +41,7 @@ decref(_Atomic(size_t)* r)
 }
 
 inline size_t
-getref(const _Atomic(size_t)* r)
+getref(const _CTL_ATOMIC(size_t)* r)
 {
     return atomic_load_explicit(r, memory_order_relaxed);
 }

ctl/shared_ptr.h

@@ -2,9 +2,18 @@
 // vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
 #ifndef COSMOPOLITAN_CTL_SHARED_PTR_H_
 #define COSMOPOLITAN_CTL_SHARED_PTR_H_
+#include "enable_if.h"
+#include "is_void.h"
 #include "new.h"
 #include "unique_ptr.h"
 
+// TODO(mrdomino): move
+#ifndef __cplusplus
+#define _CTL_ATOMIC(x) _Atomic(x)
+#else
+#define _CTL_ATOMIC(x) x
+#endif
+
 namespace ctl {
 
 // TODO(mrdomino): move
@@ -20,8 +29,8 @@ namespace __ {
 
 struct shared_control
 {
-    _Atomic(size_t) shared;
-    _Atomic(size_t) weak;
+    _CTL_ATOMIC(size_t) shared;
+    _CTL_ATOMIC(size_t) weak;
 
     constexpr shared_control() noexcept : shared(0), weak(0)
     {
@@ -91,7 +100,7 @@ struct shared_emplace : shared_control
 
     static unique_ptr<shared_emplace> make_unique()
     {
-        return new shared_emplace();
+        return unique_ptr(new shared_emplace());
     }
 
   private:
@@ -201,8 +210,9 @@ class shared_ptr
         return p;
     }
 
-    // TODO(mrdomino): fix for shared_ptr<void>
-    T& operator*() const noexcept
+    template <typename U = T>
+    typename enable_if<!is_void_v<U>, U&>::type
+    operator*() const noexcept
     {
         if (!p)
             __builtin_trap();
@@ -217,7 +227,9 @@ class shared_ptr
         return *p;
     }
 
-    element_type& operator[](ptrdiff_t i) const
+    template <typename U = T>
+    typename enable_if<!is_void_v<U>, U&>::type
+    operator[](ptrdiff_t i) const
     {
         return *(p + i);
     }

test/ctl/shared_ptr_test.cc

@@ -17,6 +17,7 @@
 // PERFORMANCE OF THIS SOFTWARE.
 
 #include "ctl/shared_ptr.h"
+#include "libc/mem/leaks.h"
 
 #include "libc/runtime/runtime.h"